Motion control and robotics integration
Controls for line-based motion control can be separate or integrated with robotics, depending on technologies used, connected networks, and sophistication of those involved.
Options for integrating robotics with other axes of motion in a work cell or a line vary depending on a number of factors, according to Bob Hirschinger, principal engineer for motion controller and software products, Rockwell Automation, who spoke to Control Engineering at RSTechED on June 17. Hirschinger provided perspectives on complex multi-axis motion control and robotics. Options could vary widely depending on the robot vendor, automation vendor, and the amount of cooperation between them, he suggested.
Multi-axis motion control, robots
Robotic and motion control programming options include, in generic terms:
1. Separate robot and motion programming. Robots operate with the robot vendor control system and kinematic software. Nonrobotic motion control would be controlled by separate hardware and separate software. Communication capabilities may vary according to capabilities of vendors' products and the sophistication of the machine builder and system integrators involved.
A line/machine controller (programmable logic controller, PLC) connects via network (typically Ethernet) to a dedicated robot controller (typically the robotic arm vendor's control/drive system), which manages robot operations. Robotic programming is accomplished with the robot vendor's programming software and teach-n-learn devices. The robot controller is often networked to a separate machine/line controller (such as a PLC). The machine/line controller manages the overall machine operation and sequencing, manages the motion of other general motion control (GMC) axes, and coordinates its operation with the robot controller through the network interface. This architecture does not have tight synchronization of the robot arm and the PLC's GMC axes. (In some cases, GMC axes that require tight coordination with the robot may have to be controlled by the robot controller.)
This architecture includes:
- Multiple controllers — machine/line PLC and robot controller
- Robot vendor's drives/motors
- Multiple software programming packages using multiple programming languages — typically IEC 61131-3 base language for the PLC and a dedicated text base language for the robot.
- NOTE: In some cases the robot vendor may support high-level instruction libraries for some PLC vendor's controllers.
- Coordination of the PLC controller resources (such as GMC axes) and robot is typically limited.
2. Integrated hardware with separate software. A controller not supplied by the robotic vendor uses the robot vendor's control software and can control other motion axes separate from the robot.
Same hardware architecture as (1) above is used, but the robot supports a "remote" host mode of operation. In the remote mode the robot motion is controller managed by the host controller, in this case the line/machine PLC with an embedded motion/kinematics instruction set.
This architecture includes:
- Multiple controllers-machine/line PLC and robot controller
- Robot vendor's drives/motors
- In the robot host mode, there's one software programming package with one programming language (typically IEC 61131-3 base language) since the robot is directly controlled by the machine/line PLC (robot motion/kinematics are managed by the machine/line PLC)
- PLC vendor may offer robotic motion control instruction libraries
- It is possible to have very tight coordination between the robot and the other resources (GMC axes) that are controlled by the line controller because all GMC and robot axes are controlled by the machine/line PLC.
3. Integrated hardware and software, bypassing the robotic vendor's control hardware and software. In this option, a controller and software not supplied by the robotic supplier controls the robot and other motion axes separate from the robot.
With this architecture you have:
- One controller-machine/line PLC
- Robot vendor's drives/motors or same drives/motors that are used on the GMC axes
- Single software programming package with a single programming language (typically IEC 61131-3 base language) since the robot is directly controlled by the machine/line PLC (robot motion/kinematics are managed by the machine/line PLC)
- PLC vendor may offer robotic motion control instruction libraries.
- It is possible to have very tight coordination between the robot and the other resources (GMC axes) that are control by the line controller because all GMC and robot axes are controlled by the machine/line PLC.
Rockwell Automation's Integrated Architecture, Hirschinger said, includes libraries of code (function-block libraries), a unified software environment, and integrated hardware to help with integration of robotics with other motion axes. Rockwell Automation has a number of robotics partners that can work with customers to select the best solution.
Preference for which method is used, Hirschinger said, depends on familiarity with the technologies, programming preferences, PLC controlled resource (GMC axes), and robot synchronization requirements.
- Mark T. Hoske is content manager, CFE Media, Control Engineering, email@example.com.
This online archive article contains additional information.
- It's possible to integrate robotic control and motion control outside the robot.
- The extent of that integration depends on software familiarity, performance required, and vendors involved, among other factors.
Would it be worthwhile to have one motion programming platform rather than separate ones for robotics and motion control?
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